<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <p class='demo'>hello JavaScript</p>
    <script>
        // 获取<p class='demo'>hello JavaScript</p>内部文案
        const demo = document.getElementsByClassName("demo");
        console.log(demo[0].innerText);
    </script>
</body>
</html>